Method of making a surgical cast



United States Patent METHOD OF MAKING A SURGICAL CAST Philip Leslie,Leeds, Frederick J. R. Batten, Morley, and Ernest W. Smith, Dewsbury,England No Drawing. Application June 7, 1955 Serial No. 513,892

10 Claims. (Cl. 128-90) This invention relates to a method of preparingrigid supporting means and the main aspect of the invention is concernedwith the preparation of surgical casts or splints.

Hitherto, the most widely used method of immobilising and supportingparts of the human body, has been to employ casts formed with plaster ofParis. This method involves the preparation of bandages in the form ofplaster coated strips of cotton fabric, dipping these'strips in Water,applying the moistened bandages around the appropriate part of the bodyand allowing the plaster to dry and set after which it will act as arigid supporting means. Casts formed by this method, however, havecertain disadvantages in that they are absorbent to fluids includingliquids secreted from the body, they are comparatively heavy, they takea long time to set during which time adverse therapeutic conditions areliable to be established, they are substantially impervious toelectrical rays, and, in the course of absorbing fluid, they areweakened.

In an effort to overcome the disadvantages inherent in the plaster ofParis type of cast, it has been proposed to form an entirely differentkind of support by the method of applying to the part of the body to beimmobilised, layers of fabric having threads which comprise solubleplastic material, treating the fabric with a solution which exerts aWeak solvent action on the material and'has a saturation value thereforof less than 300 milligrams per 100 cubic centimeters of treatingsolution at 70 degrees Fahrenheit, and allowing the fabric to form intothe shape desired and, upon removal of the solvent, to become set andrigid. I

Though a surgical cast formed in this manner possesses many advantagesover the conventional plaster of Paris cast, the threads of the fabricwhen treated with solution of the kind specified contract to anextent'suflicient in many cases to occasion severe discomfort to'thepatient. It has been proposed, in order to overcome this difiiculty, toinclude in the method set forth,the step of shrinking the fabric priorto treatment with the specified weak solvent solution. Alternatively, ithas been proposed to utilise fabrics which, in addition to threadsformed with soluble plastic material, contain threads which are inert tothe action of the solvent solution.

The difiiculty has, however, arisen that, in the case of a fabricconsisting of threads of soluble plastic material,

' irrespective of the manner in which the fabric has been shrunk,subsequent treatment of the fabric with weak solvent solution of thekind specified has resulted in casts having inadequate rigidity.Furthermore, the use of fabrics having inert threadsdoes not resolve thedifficulty in an entirely satisfactory manner and involves aconsiderable increase in cost as such fabrics are relatively veryexpensive to produce.

It is an object of the present invention to provide a method of forrningimproved supporting means from fabrics consisting of threads comprisingsoluble plastic 2,847,992 Patented Aug. 19, 1958 material. A furtherobject of the invention is to provide rigid supporting means atrelatively low cost.

The features of novelty characterising our invention are pointed out inthe claims annexed to and forming part of the present specification. Theabove and further objects and advantages of the invention will beapparent from the following description in which we have describedpreferred embodiments of our invention.

The invention finds its widest application in the sphere of medicinewhere it is used in the formation of rigid surgical supports.Preferably, in the formation of such supports, on the part of the bodyto be supported, are wound a couple of layers of the fabric consistingof threads containing over percent of cellulose acetate. The layers offabric so mounted are treated with a solvent solution which has asaturation value for cellulose acetate of less than 300 milligrams percubic centimeters of solution. The analyses by weight of three suitablesolutions which fall within this range are as follows:

Example (a) Percent Methanol 35.50 Isopropyl alcohol 35.43 Dimethylketone 28.55 Formaldehyde 0.25 Diacetone alcohol 0.15 Benzaldehyde 0.10

the balance being colour and perfume. Example (b):

Methanol 33.43 Ethanol 15.50 Methyl ethyl ketone 35.20 Benzyl alcohol10.55 Acetaldehyde 3.20 Benzaldehyde 2.07

the balance being colour and perfume. Example (0):

Ethanol 61.04 Isoamyl alcohol 7.27 Formaldehyde 1.15 Dimethyl ketone25.50 Methyl isobutyl ketone 4.55 Diacetone alcohol 0.33 Acetophenone0.12

the balance being colour and perfume.

After treatment with one of the abovementioned solutions the layers areallowed to dry for about half a minute and a further couple of layersare wound over the layers first applied and the process of treatmentwith the solution is repeated. In this way an appropriate.number oflayers of processed fabric is applied to the part of the body which isto be immobilised. In the case of minor casts utilised, for example, forirnmobilising fingers or toes, six layers of fabric will normallyprovide a cast of adequate strength. However, for major casts utilised,for example, to immobilise arms or legs, between eight and twelve layersof fabric are usually required. The solutions quoted in Examples a, b orc are applied so as to effect shortening of the threads of the fabricand in the interests of economy, can, advantageously, be applied bymeans of a sponge or brush. When a sufficient number of layers ofmaterial have been applied and treated as described above with one ofthe relatively weak solvent solutions of Examples a, b or c, thematerial is then subjected to treatment with a relatively strongsolution having a saturation value for cellulose acetate of between 400and 100,000 milligrams per 100 cubic centimeters of solution at 70degrees Fahrenheit. The analyses by weight of three relatively strongsolvent solutions falling within the desired solubility range are asfollows:

Example 1:

Percent Ethanol 5.40 Isoamyl alcohol 0.75 Formaldehyde 1.15 Dimethylketone 87.50 Methyl isobutyl ketone 4.75 Diacetone alcohol 0.33Acetophenone 0.12

the balance being colour and perfume.

Example 2:

Methanol 5.50 Isopropanol 5.45 Dimethyl ketone 88.55 Formaldehyde 0.25Diacetone alcohol 0.15 Benzaldehyde 0.10

the balance being colour and perfume.

Example 3:

Methanol 3.50 Ethanol 1.55 Methyl ethyl ketone 92.15 Benzyl alcohol 1.55Acetaldehyde 0.35 Benzaldehyde 0.90

the balance being colour and perfume.

After the fabric layers have been treated with one of the relativelystrong solvent solutions enumerated above, they are allowed to drywhereupon they form a cast which is sufficiently rigid, comparativelylight in Weight, permeable to electrical rays and waterproof.

Both in Examples a, b and c, and Examples 1, 2 and 3, it is the ketonecomponent which acts as the main solvent for the cellulose acetate inthe threads of the fabric whilst the remaining components serveprincipally as diluents.

The action on a fabric consisting of threads comprising soluble plasticmaterial of a solvent solution which in respect of such material has asaturation value at 70 degrees Fahrenheit of between 400 and 100,000milligrams per 100 cubic centimeters of solution, results, in the caseof a fabric which has not been processed so as to shorten its threads,in at least a partial breakdown of the fabric which arises from thetendency of its threads, under the influence of the solution, to flow.However, in the method according to the present invention the action ofsolvents having relatively higher saturation values than those employedhitherto on fabrics processed so as to shorten the threads thereof doesnot occasion any appreciable breakdown of the said threads. Theexplanation of this phenomenon is thought to reside both in the factthat the increased density of the soluble plastic material of thethreads which is evident after contraction thereof, reduces theavailability to the solvent of the soluble plastic material also, andparticularly where the desired processing of the threads is broughtabout by treatment, as hereinbefore set forth, with solvent solutionhaving a relatively low saturation value, one of the physical changeswrought in the fabric during the processing thereof is such as toproduce a reduced capillary attraction of the fabric for the solventsolution, which, in view of the volatility of the solvent solution,makes for reduced action by the solvent and suggests that effectivefurther plasticising of the fabric will require the use of solventshaving relatively higher saturation values. Another factor to be takeninto account is that the contraction effected in the threads isaccompanied by a certain thickening thereof which renders the threadsable to withstand subsequent application of solvents having relativelyhigh saturation values without appreciably breaking down.

Though, the processing of the fabric for the purpose of shortening itsthreads may be carried out by heat treatment under controlledconditions, the processing is effected, preferably, by treatment with asolvent solution which has a saturation value for the soluble plasticmaterial of less than 300 milligrams per cubic centimeters of solutionat 70 degrees Fahrenheit.

The nature of the fabric to be employed depends on the type of supportto be formed. For example, in accordance with a feature of the inventiona splint can be secured and supported against a part of the body inorder to immobilise the part and the supporting means may include arelatively thin and relatively closely knit or woven fabric. A suitablefabric would be one formed with a lock knit stitch and comprisingacetate yarn of 75 denier weight. If, on the other hand it is intendedthat the fabric shall provide the sole support, though a relatively thinfabric of the kind set forth is preferable, a relatively thick andrelatively loosely knitted fabric may be used, a suitable example beinga fabric comprising yarn of denier weight and formed with a knittedsleeve stitch.

Thus the invention also includes the method of forming a rigid supportby locating a splint alongside the part of a body upon which the supportis to be formed, and, in desired sequence, binding the splint to thepart with a fabric consisting of threads comprising soluble plasticmaterial which are processed so as to shorten said threads, and treatingthe fabric with a volatile solution which exerts a solvent action on thesoluble plastic material of threads of the fabric, which has, in respectof the said material, a saturation value, at 70 degrees Fahrenheit, ofbetween 400 and 100,000 milligrams per 100 cubic centimeters of thetreating solution and which is allowed to evaporate whilst the fabric isin position on the part.

It will be appreciated that the processing of the fabric for the purposeof shortening its threads may be carried out prior to the mounting ofthe fabric on the part to be immobilised since the heating of the fabricor/ and the treatment thereof with Weak solvent solution does notdeprive the fabric, to an appreciable extent, of its flexibility.

It is desirable, when using a relatively thin fabric of the kindspecified in the case where the processing of the fabric for the purposeof shortening its threads is carried out prior to the applicationthereof to the part to be immobilised, to double the thickness thereofprior to the shrinking process during which the adjacent layers offabric become bonded together.

The measurement of the saturation value of a particular solvent mayreadily be determined by placing in a known volume of solvent solutioncontained within an appropriate vessel an excess of the soluble plasticmaterial in finely divided form, preventing the solution fromevaporating by keeping the vessel closed and allowing the solvent to actover a period of several hours, the ambient temperature being maintainedat 70 degrees Fahrenheit. The saturated solvent solution may then befiltered off and evaporated to dryness. After evaporation the residue isweighed and the saturation value may then be estimated.

Supporting means, according to the present invention, are posssessed ofadequate rigidity and are relatively cheap to produce since they involvethe use of fabrics the threads of which are of the same material. Alsothey are light in weight and of inconsiderable volume. Furthermore, suchsupporting means are waterproof and permeable to electrical rays.

Though the invention is principally concerned with the formation ofrigid surgical supporting means, the methods set forth above can beutilised, because of the Waterproof nature of the casts so formed, foreffecting temporary repairs in broken pipes. Accordingly, the supportsdescribed can be used to seal a crack in a pipe or to join the brokenends of a pipe together provided the pipe,

during service, is not subjected to inordinately high temperatures. l e

What we claim is:

1. The method of forming a rigid supporting means, which includes thesteps of processing a fabric consisting of threads comprising cellulosederivative material by treating a fabric with a volatile solution whichexerts a solvent action on the soluble plastic material of the fabricand which has in respect of the said material a saturation Value at 70degrees Fahrenheit of less than 300 milligrams per 100 cubic centimetresof the solution, and applying at least one layer of the fabric to thepart of a body upon which thesupporting means is to be formed, thesesteps being carried out in desired sequence, and, subsequently, treatingthe fabrics so processed and mounted in position with a volatilesolution which exerts a solvent action on the cellulose derivativematerial of the threads of the fabric, which has, in respect of the saidmaterial a saturation value at 70 degrees Fahrenheit, of between 400 and100,000 milligrams per 100 cubic centimetres of the treating solutionand which is allowed to evaporate whilst the fabric is in position onthe part.

2. The method as claimed in claim 1, wherein the processing of thefabric is carried out by treating the fabric with a volatile solutionhaving substantially the following composition by weight:

Percent Methanol 35.50 Isopropyl alcohol 35.43 Dimethyl ketone 28.55Formaldehyde 0.25 Diacetone alcohol 0.15 Benzaldehyde 0.10

the balance being colour and perfume.

3. The method as claimed in claim 1, wherein the processing of thefabric is carried out by treating the fabric with a volatile solutionhaving substantially the following composition by weight:

the balance being colour and perfume.

6 cessed and mounted fabric is treated with a volatile solution havingthe following composition by weight:

Percent Methanol 5.50 Isopropanol 5.45 Dimethyl ketone 88.55Formaldehyde 0.25 Diacetone alcohol 0.15 Benzaldehyde 0.10

the balance being colour and perfume.

7. The method as claimed in claim 1, wherein the processed and mountedfabric is treated with a volatile solution having the followingcomposition by weight:

Percent Methanol 3.50 Ethanol 1.55 Methyl ethyl ketone 92.15 Benzylalcohol 1.55 Acetaldehyde 0.35 Benzaldehyde 0.90

the balance being colour and perfume.

8. The method as claimed in claim 3, wherein the processing of thefabric is carried out by treating the fabric with a volatile solutionhaving substantially the following composition by weight:

the balance being colour and perfume, and the processed and mountedfabric is treated with a volatile solution, having the followingcomposition by weight:

Percent Ethanol 5.40 Isoamyl alcohol 0.75 Formaldehyde 1.15 Dimethylketone 87.50 Methyl isobutyl ketone 4.75 Diacetone alcohol 0.33Acetophenone 0.12

4. The method as claimed in claim 1, wherein the processing of thefabric is carried out by treating the fabric with a volatile solutionhaving substantially the following composition by weight:

Percent Ethanol 61.04 Isoamyl alcohol 7.27 Formaldehyde 1.15 Dimethylketone 25.50 Methyl isobutyl ketone 4.55 Diacetone alcohol 0.33Acetophenone 0.12

the balance being colour and perfume.

5. The method as claimed in claim 1, wherein the processed and mountedfabric is treated with a volatile solution having the followingcomposition by weight:

the balance being colour and perfume.

6. The method as claimed in claim 1, wherein the prothe balance beingcolour and perfume.

9. The method as claimed in claim 1, wherein the processing of thefabric is carried out by treating the fabric with a volatile solutionhaving substantially the following composition by weight:

Percent Methanol 33.43 Ethanol 15.50 Methyl ethyl ketone 35.20 Benzylalcohol 10.55 Acetaldehyde 3.20 Benzaldehyde 2.07

the balance being colour and perfume, and the processed and mountedfabric is treated with a volatile solution, having the followingcomposition by weight:

the balance being colour and perfume.

10. The method as claimed in claim 1, wherein the processing of thefabric is carried out by treating the 7 fabric with a volatile solutionhaving substantially the following composition by weight:

Percent Ethanol 61.04 Isoamyl alcohol 7.27 Formaldehyde 1.15 Dimethylketone 25.50 Methyl isobutyl ketone 4.55 Diacetone alcohol 0.33 0.12

Acetophenone the balance being colour and perfume, and the processedhaving the following composition by weight:

Percent Methanol 3.50 Ethanol 1.55 Methyl ethyl ketone. 92.15 Benzylalcohol 1.55 Acetaldehyde 0.35 Benzaldehyde 0.90

the balance being colour and perfume.

References Cited in the file of this patent UNITED STATES PATENTS2,308,483 Anderson Jan. 19, 1943 2,373,802 Anderson Apr. 17, 19452,489,252 7 Anderson Nov. 29, 1949 2,632,442 Anderson Mar. 24, 1953

1. THE METHOD OF FORMING A RIGID-SUPPORTING MEANS, WHICH INCLUDES THESTEPS OF PROCESSING A FABRIC CONSISTING OF THREADS COMPRISING CELLULOSEDERIVATIVE MATERIAL BY TREATING A FABRIC WITH A VOLATILE SOLUTION WHICHEXERTS A SOLVENT ACTION ON THE SOLUBLE PLASTIC MATERIAL OF THE FABRICAND WHICH HAS IN RESPECT OF THE SAID MATERAIL A SATURATION VALUE AT 70DEGREES FAHRENHEIT OF LESS THAN 300 MILLIGRAMS PER 100 CUBIC CENTIMETERSOF THE SOLUTION AND APPLYING AT LEAST ONE LAYER OF THE FABRIC TO THEPART OF A BODY UPON WHICH THE SUPPORTING MEANS IS TO BE FORMED, THESESTEPS BEING CARRIED OUT IN DESIRED SEQUENCE, AND, SUBSEQUENTLY, TREATINGTHE FABRICS SO PROCESSED AD MOUNTED IN POSITION WITH A VAOLATILESOLUTION WHICH EXERTS A SOLVENT ACTION ON THE CELLULOSE DERIVATIVEMATERIAL OF THE THREADS OF THE FABRIC, WHICH HAS, IN RESPECT OF THE SAIDMATERIAL A SATURATION VALUE OF 70 DEGREE FAHRENHEIT, OF BETWEEN 400 AND100,000 MILLIGRAMS PER 100 CUBIC ENTIMETERS OF THE TREATING SOLUTION ANDWHICH IS ALLOWED TO EVAPORATE WHILST THE FABRIC IS IN POSITION ON THEPART.